Kaushitakagrihyasutra 2.2.15

2.2.15

tenaiva mantreṇa tathaiva paryāvṛtya dakṣiṇena prādeśena dakṣiṇaṃ bāhumanvārabhyāha brahmacāryasi samidhamādhehi apo 'śāna karma kuru divā mā suṣupthāḥ vācaṃ yacchā samidādhānāt \15\

With that very formula, having turned around in that same way, touching his right arm with his right hand stretched from thumb to forefinger, he says: 'You are a Vedic student; put on kindling wood; sip water; do the work; do not sleep during the day; restrain your speech until the putting on of kindling wood.'